1. Field of the Invention
The present invention relates to tunable lasers, and particularly to a temperature tuned conjugated polymer laser that uses a thiophene-based conjugated polymer as the laser medium.
2. Description of the Related Art
There is a great deal of interest in optically-pumped tunable lasers, since such lasers have a very broad range of applications, from industrial purposes to medical applications. However, optically pumped, tunable solid-state lasers, such as Ti:sapphire and forsterite lasers, although presently commercially available, are both expensive and have limited tunability. Presently, research is being directed towards dye lasers, which use such dyes as rhodamine and coumarin derivatives as a lasing medium, since such dye-based laser media have an excellent capacity for tunability. However, such dyes have, thus far, been found to have shortcomings related to their photochemical stability.
In order to find an alternative to such dyes as rhodamine and coumarin derivatives, conjugated polymers have been proposed as a potential new type of laser material, since conjugated polymers should exhibit better photochemical stability than conventional dye solutions. Conjugated polymers contain alternating C═C double bonds (typically one σ-bond and one π-bond) and C—C single bonds (σ-bonds). This alternation of single and double bonds determines the opening of the band gap due to the Peierls distortion and explains why conjugated polymers in their neutral state are semiconductors and not metals. As a result of the oscillation of the π-electrons, electromagnetic radiation is absorbed. The process is similar to what occurs during the photosynthesis process in plants. For example, a molecule with only one conjugated double bond will absorb only ultraviolet light. With additional conjugated double bonds, a molecule will be able to absorb different wavelengths of visible light. The π-electrons are therefore responsible for determining the electrical and chemical properties.
There are many types of conjugated polymer based on building block materials (i.e., monomers) such as polypyrrole, polyaniline, polythiophene and polyacetylene. One such polymer group is the polythiophenes, which possess unique electrical and optical properties, and which have been shown to have very good thermal stability and fluorescence properties. They have found application in many fields, such as OLEDs, solar cells, and biosensors. Thus, a temperature tuned conjugated polymer laser solving the aforementioned problems is desired.